Double-Layer Cathode Structure for High-Energy Battery Stability
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Solution Overview
Problem
Current high-energy density electrochemical devices face challenges in enhancing safety performance and cycle stability due to limitations in cathode material design and structure, which can lead to reduced kinetic performance and energy density when attempting to improve thermal and structural stability.
Innovation Solution
A cathode with a multilayer structure comprising a current collector, a first material layer, and a second material layer, where the second material layer, including phosphate or lithium titanium phosphate, is positioned between the current collector and the first material layer, providing improved voltage protection, structural stability, and reduced interfacial reaction damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a cathode material with high energy density is used to improve the energy density of the electrochemical device, then the energy density is improved, but the safety performance requirements become higher and safety performance deteriorates
Solution Approach 1:
A protective coating layer comprising phosphate (M1PO4) or lithium titanium phosphate (Li3Ti2-xM2x(PO4)3) is applied to the surface of the cathode active material particles. This coating layer acts as an intermediary barrier between the high-energy-density cathode material and the electrolyte, preventing direct harmful interactions while allowing ionic transport, thereby improving safety performance without compromising energy density
Solution Approach 2:
The cathode structure is designed as a composite material system combining the high-energy-density cathode active material (such as lithium nickel cobalt manganese oxide) with a protective coating layer of phosphate or lithium titanium phosphate. This composite structure leverages the high capacity of the core material while the coating provides enhanced safety and stability, resolving the contradiction between energy density and safety performance
2Reliability
If doping or coating is applied to change thermal stability and structural stability, then safety performance is improved, but kinetic performance, cycle performance and energy density deteriorate
Solution Approach 1:
The coating layer parameters are precisely controlled including thickness (1-10 nm), composition ratios (M1:PO4 or Li3Ti2-xM2x(PO4)3 stoichiometry), and crystalline structure. By optimizing these parameters, the coating provides adequate thermal stability while maintaining sufficient ionic conductivity to preserve kinetic performance and energy density
Solution Approach 2:
The protective coating is applied selectively on the surface of cathode active material particles rather than uniformly throughout the entire cathode structure. This localized approach ensures thermal stability at the particle surface where it is most needed, while minimizing the impact on bulk ionic transport and kinetic performance
3Duration of action of stationary object
If inert additive or surface additive is added to electrolytic solution to form interfacial film for cycle stability, then cycle performance is improved, but kinetic performance and energy density deteriorate
Solution Approach 1:
Instead of adding additives to the electrolyte to form interfacial films, the patent applies a protective coating layer directly to the cathode active material surface. This coating acts as a stable intermediary that provides long-term cycle stability without interfering with electrolyte composition or requiring additional additives that would compromise kinetic performance and energy density
Data Source
AI summary
A cathode includes a current collector, a first material layer and a second material layer. The first material layer includes a first material. The second material layer includes a second material. The second material includes at least one of the followings compounds: phosphate represented by a general formula M1PO4 and lithium titanium phosphate represented by a general formula Li3Ti2-x M2x(PO4)3, and the second material layer is disposed between the current collector and the first material layer. The cathode of the present application is provided with a double-layer structure including at least one of phosphate and lithium titanium phosphate to avoid direct contact between the current collector in the cathode and an anode material layer and optimize the stability of the first material layer, so that the cycle performance, electrochemical stability and safety performance of the electrochemical device are significantly improved.